My engine won't start?

Engine Mechanical problem V8 Two Wheel Drive Automatic

5.7L Vortec Engine and it's a van. It has had a history of hard time starting the vehicle. It would turn but hard time starting. Now won't start. I've changed spark plugs and rotor and distributor cap and it started (but not easy). Then I changed ignition wires. Then it won't start. It is getting fuel out of fuel port (splashes out if I open and press it for a split second) and it is getting spark at the spark plug wires. I can rotate the distributor slightly if I force it with hand so I am thinking it could be timing issue. I would back fire occasionally as it wants to start sometimes. So maybe it is misfiring. What are other components that I should check?


Fuel Pressure is reading slightly above 60 psi which is within factor spec (60 - 60 psi).

Current Status:
It backfires as frequently as it tries to start. Occasionally, the engine would turn then very briefly pause (hesitate) slightly and then keep cranking. The inside light would dim slightly when it does this.

Other note:
Fuses were checked and they seemed to be all fine. No code comes out when I read the ECU with the OBD reader.

Caveat Note:

When I changed spark plug wires, I did accidentally broke coolant temperature sender wire (for gauge, not ECU). I spilled coolant all over the places. I did reinstall brand new sensor to make sure it is not the cause of the problem. That was couple of days ago and coolant being slightly spilled over to the side are all dried up by now. I did unplug couple of wires and let it dry to make sure. I did refill coolant on overflow to the top but not main one since I have to break the coolant cap to refill the coolant.

Here are some of my possibilities that I can think of but it would be great if I knew which direction to go first.

1. FUEL ISSUE.

Clogged fuel injectors or some other fuel issue. I am thinking this because I did find pretty good amount of black deposits in the throttle body. I did clean them off with carb cleaner by spraying them few days ago. The van did start after I did this operation.

2. TIMING ISSUE

The distributor rotor moves slightly if I hold it firm and turn it. So I am concerned with timing.

3. SPARK ISSUE

I am not sure if I am getting weak spark or good spark. It looks good spark to me as I tested it with spark plug tester. It is hard to tell without more accurate equipment. So perhaps coil might be failing?